The main physiological cue for migration will be the changes while in the day size. These modifications are connected with hormonal improvements during the birds. From the time period prior to migration, lots of birds display increased activity or Zugunruhe (German: migratory restlessness), 1st described by Johann Friedrich Naumann in https://petskyonline-cat-shop88433.blogdigy.com/5-easy-facts-about-pet-bird-care-uae-described-58112452